Generate the hexadecimal representation for a given non-negative integer number as a string. The hex representation should start with "0x".

There should not be extra zeros on the left side.

Examples

• 0's hex representation is "0x0"
• 255's hex representation is "0xFF"

Solution: 注意0

  public String hex(int number) {
    if (number == 0) {
      return "0x0";
    }
    StringBuilder sb = new StringBuilder();
    while (number > 0) {
      int remain = number % 16;
      if (remain > 9) {
      //要有强制转换
        char c = (char)(remain - 10 + 'A');
        sb.append(c);
      } else {
        sb.append(remain);
      }
      number /= 16;
    }
    sb.append("x0");
    int i = 0, j = sb.length() - 1;
    //或者直接sb.reverse()
    while (i < j) {
      char temp = sb.charAt(i);
      sb.setCharAt(i, sb.charAt(j));
      sb.setCharAt(j, temp);
      //记得i++, j-- !!
      i++;
      j--;
    }
    return sb.toString();
  }